Devices are known having the shape of pistols and made for introducing medicinal substances inside animals.
A particular type of these devices comprises a base body having a handle for gripping by the user.
Inside the base body, a hollow injection needle is fitted, in the proximity of which a cartridge is associable containing one or more doses of medicinal substances in the form of pellets, i.e., small cylindrical capsules, to be introduced into the animal.
The cartridge has a series of cavities containing the pellets and alignable with the hollow needle to be crossed longitudinally by a mobile push rod.
The push rod is fitted on a carriage sliding longitudinally and which can be operated forwards and backwards manually by the user by means of a bayonet mechanism.
The bayonet mechanism appears out of the top of the base body to allow it to be gripped by the user and is connected to the sliding carriage.
By means of the bayonet mechanism, the carriage is made to slide backwards and then forwards.
The forward stroke of the carriage is split into two sections.
During the first section, the hollow needle remains at a standstill while the push rod crosses a cavity of the cartridge and transfers the pellets inside the hollow needle.
During the second section, instead, a push mechanism is triggered that drags forward not only the push rod but also the hollow needle, as far as a blockage position.
At the time of dispensing, the hollow needle is introduced into the animal and, by means of the operation of a release trigger, the hollow needle returns to departure position while the push rod remains at a standstill, ensuring the pellets stay inside the animal and are not dragged by the hollow needle.
Inside the hollow needle, a tubular element is fitted that guides the exit of the pellets and is made to retain these when, once pushed out of the cartridge, they are inside the hollow needle and have to be injected into the animal.
For this purpose, the tubular element has an exit extremity the edge of which is carved and slightly folded towards the inside of the tubular element itself.
The exit extremity made this way therefore has a shape similar to that of a truncated cone.
This device of known type has a number of drawbacks including the fact that the tubular element arranged inside the hollow needle is not able to operate efficiently and reliably for very long.
After being used just a few times in fact, it loses its shape memory and takes on an almost perfectly cylindrical configuration which does not help in any way to retain the pellets inside the hollow needle before these are introduced into the animal.
It often occurs therefore that once the bayonet mechanism has been loaded and the hollow needle has been filled with the pellets to be injected, the latter come out of the hollow needle due to simple gravity.
To overcome this problem, the user is forced to inconveniently always keep the pistol turned upwards, which strongly restricts his/her freedom of movement precisely during the most delicate stage of the operation, i.e., the injection of the hollow needle inside the animal.
To this must be added that the push rod and hollow needle operating system is rather complicated from a constructive and structural viewpoint and very often ends up jamming or producing other operating problems.
Furthermore the use of a bayonet mechanism involves the presence of a gripping knob sliding along the base body and stoppable in an end-of-stroke position, where the gripping knob must be turned on the right side of the pistol.
The gripping knob is therefore very inconvenient to use by left-handed users, which strongly restricts the operating practicality of the entire device.
Another drawback consists in the fact that the device handle, i.e., the butt of the pistol, is located a long way from the hollow needle, i.e., in a particularly retracted position.
Because of this, the manoeuvrability and the stability of the pistol, above all when aiming the hollow needle at the animal and injecting the pellets, is very limited.
Neither should it be forgotten that only one cartridge at a time can be loaded in this pistol, forcing the user to inconveniently have to use a cartridge strap or separate cartridge holder.
This latter drawback is particularly felt in all farms comprising a large number of heads of cattle, where the substances contained in a single cartridge are very quickly finished and where the used cartridges have to be frequently changed with serious loss of time, which inevitably translates into limited productivity and into an inconvenient increase in labour costs.